Athletes and persons wishing to monitor their health often desire to obtain or monitor data pertaining to their physical activities, accomplishments, or condition. In some situations, a physician may prescribe certain steps or exercise to be performed by a patient under certain conditions, such as performing an exercise at or near a certain heart rate. The doctor and/or the patient may wish to gather data regarding the performance of the exercise, the conditions under which the exercise was performed, and/or how the patient is responding to the exercise. An athlete may wish to gather and monitor details about his or her physical performance in a similar manner. For example, an athlete who can correlate different training or exercise techniques with improved performance metrics can become faster, stronger, or exert more force in an action, such as hitting a ball harder. Athletes, patients, and anyone else associated with a physical activity can benefit from improved techniques for gathering, monitoring, correlating, analyzing, using, interpreting, and making decisions based on physical activity data